1. Field of the Invention
The invention is concerned with dental impression trays which may be extended or contracted to adjust for the specific size and configuration of individual patient's mouths and in preferred forms may be used to take impressions of the upper and lower arches simultaneously.
2. Prior Art
A current type of impression tray that is widely used consists of a pair of spaced apart vertical plastic walls joined by a horizontal mesh and having a gripping area at the anterior end and most often a posterior strap or loop joining the walls at the posterior ends of the walls. The dentist must stock a large number of different sizes to accommodate the vagaries of different patient mouths. The present tray in contrast is easily adapted to variations in the dental arch.
U.S. Pat. No. 4,145,812--Johnson discloses an adjustable dental impression tray in which an extension piece telescopes over secondary leg portions of the primary unit. Flap and tab combinations hold the adjusted extension in a selected position.
U.S. Pat. No. 4,368,040--Weissman shows a complex tray with grooved sides for holding an elongated strap.
U.S. Pat. No. 2,529,429--Spiro discloses a two-part tray held together with a hinge. The relative movement of the two parts is up and down and the purpose is to place additional pressure on the impression taking compound.
U.S. Pat. No. 3,890,711 of the present applicant concerns an adjustable dental impression tray including a primary unit and a slidable unit mounted telescopically on the primary unit with a T shaped slot and elongated slot and securing means including a mounting head and threaded stem going through both slots and a retainer head on the projecting end of the stem to hold the securing means together. This tray is useful, however, the securing means is somewhat complex in construction and requires intense concentration to use. Further, the invention therein is not readily adaptable to use with the plastic wall and mesh devices currently in wide use.
Of background interest are the following references relating to early developments in adjustable dental trays. U.S. Pat. Nos. 753,679 of Mar. 1, 1904; 755,670 of Mar. 29, 1904; 765,919 of Jul. 26, 1904; 1,054,999 of Mar. 4, 1913; 1,493,417 of May 6, 1924; 2,426,388 of Aug. 26, 1947; Swiss Pat. No. 57,395 of Jul. 21, 1911 and German Pat. No. 1,083,017 of Jun. 9, 1960.
None of these devices disclosed provide the simplicity of construction, the control and locking of the relatively adjustable parts, and resulting ease of use of my invention for taking dual dental impressions simultaneously.